A plan to set up a next-generation power network (smart grid system) has been developed in order to stabilize the quality of power by using exhaustible energy based on nuclear power, thermal power, etc. together with renewable energy based on sunlight, wind power, etc.
In the next-generation power network, a system device such as an EMS (Energy Management System) is connected to the Internet to perform maintenance and to predict power demand. However, the Internet is threatened with computer viruses, information leak, illegal access, etc. Accordingly, there is a likelihood that such a system device as the EMS connected to the Internet causes problems with information security.
For example, conventional techniques generally used to prevent illegal access includes a technique of installing an intrusion detection system (IDS) on the network or EMS, and a technique of periodically applying patches for dealing with vulnerability (security defects). However, the system device, particularly the EMS, is different from a conventional server device such as a Web server in that the system device acquires information about electric generating capacity etc. from a device such as a remote terminal unit (RTU) through a power system network, and periodically transmits command signals for e.g. generating power at regular time intervals. Thus, restrictions on latency should be considered. Accordingly, it is impractical to perform such a complicated and heavily-loaded process as detecting illegal access by the system device. It is desirable that the system device can prevent illegal access from the Internet without affecting the original power control.